Eye therapy system

ABSTRACT

A system for applying therapy to an eye selectively applies coolant to the corneal surface to minimize heat-related damage to the corneal surface during thermokeratoplasty. Embodiments may include an energy source, a conducting element, a coolant supply, and a coolant delivery system. The conducting element is operably connected to the energy source and extends from a proximal end to a distal end. The conducting element directs energy from the energy source to the distal end, which is positionable at the eye. The coolant delivery system is in communication with the coolant supply and is operable to deliver a micro-controlled pulse of coolant to the distal end.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 12/208,963,now U.S. Pat. No. 8,202,272, titled “Eye Therapy System” and filed Sep.11, 2008, which is a Continuation-In-Part (CIP) Application of U.S.application Ser. No. 11/898,189, titled “Eye Therapy System” and filedSep. 10, 2007, which claims the benefit of U.S. Provisional ApplicationNo. 60/929,946, titled “Commercialization Of MicrowaveThermokeratoplasty” and filed Jul. 19, 2007, the contents of theseapplications being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to the field of keratoplasty and, moreparticularly, to thermokeratoplasty and the application of coolant tothe eye during thermokeratoplasty.

2. Description of Related Art

A variety of eye disorders, such as myopia, keratoconus, and hyperopia,involve abnormal shaping of the cornea. Keratoplasty reshapes the corneato correct such disorders. For example, with myopia, the shape of thecornea causes the refractive power of an eye to be too great and imagesto be focused in front of the retina. Flattening aspects of the cornea'sshape through keratoplasty decreases the refractive power of an eye withmyopia and causes the image to be properly focused at the retina.

Invasive surgical procedures, such as laser-assisted in-situkeratomileusis (LASIK), may be employed to reshape the cornea. However,such surgical procedures typically require a healing period aftersurgery. Furthermore, such surgical procedures may involvecomplications, such as dry eye syndrome caused by the severing ofcorneal nerves.

Thermokeratoplasty, on the other hand, is a noninvasive procedure thatmay be used to correct the vision of persons who have disordersassociated with abnormal shaping of the cornea, such as myopia,keratoconus, and hyperopia. Thermokeratoplasty may be performed byapplying electrical energy in the microwave or radio frequency (RF)band. In particular, microwave thermokeratoplasty may employ a nearfield microwave applicator to apply energy to the cornea and raise thecorneal temperature. At about 60° C., the collagen fibers in the corneashrink. The onset of shrinkage is rapid, and stresses resulting fromthis shrinkage reshape the corneal surface. Thus, application of heatenergy in circular or ring-shaped patterns around the pupil may causeaspects of the cornea to flatten and improve vision in the eye. However,devices for thermokeratoplasty generally apply energy through thecorneal surface to heat the underlying collagen fibers. Therefore, themaximum temperature can occur at the corneal surface, resulting inpossible heat-related injury and damage to the outer layer, known as theepithelium, at the corneal surface. Moreover, devices forthermokeratoplasty may provide inadequate approaches for controlling thedepth of heating below the corneal surface and promoting sufficientheating of the targeted collagen fibers while minimizing the applicationof heat to areas outside the targeted collagen fibers.

SUMMARY OF THE INVENTION

In view of the foregoing, embodiments of the present invention provide asystem that selectively applies coolant to the corneal surface tominimize heat-related damage to the corneal surface duringthermokeratoplasty and to determine the depth of heating below thecorneal surface.

Accordingly, an embodiment of the present invention includes an energysource, a conducting element, a coolant supply, and at least one coolantdelivery element. The conducting element is operably connected to theenergy source and extends from a proximal end to a distal end. Theconducting element directs energy from the energy source to the distalend, which is positionable at an eye. The coolant delivery elements arein communication with the coolant supply and are operable to deliver amicro-controlled pulse of coolant to the distal end.

Another embodiment includes an electrical energy source, an electricalenergy conducting element, a coolant supply, and at least one coolantdelivery element. The electrical energy conducting element includes twoconductors that are separated by a gap of a selected distance and thatextend from a proximal end to a distal end. The electrical conductingelement, which is operably connected to the electrical energy source,receives, at the proximal end, electrical energy generated by theelectrical energy source and directs the electrical energy to the distalend, which is positionable at an eye. The coolant delivery elements arein communication with the coolant supply and are operable to deliver amicro-controlled pulse of coolant to the distal end.

A particular embodiment includes an electrical energy source and anelectrical energy conducting element extending from a proximal end to adistal end. The energy conducting element is operably connected to theelectrical energy source at the proximal end and adapted to directelectrical energy to the distal end. The energy conducting elementincludes an outer conductor extending to the distal end and an innerconductor extending to the distal end and disposed within the outerconductor, where the outer conductor and the inner conductor areseparated by a gap. In this embodiment, the inner conductor has anopening at the distal end and a contact area along a periphery of theopening. The contact area is positionable at a surface of an eye, andthe electrical energy is applied to the eye according to the contactarea. The outer conductor and the inner conductor may be substantiallycylindrical at the distal end, and the gap may be a substantiallyannular gap with a radial thickness of approximately 0.5 mm toapproximately 1.5 mm. The contact area may also be a substantiallyannular surface with a radial thickness in a range of approximately 50μm to approximately 200 μm. The opening at the distal end may be definedby a hollow portion extending into the inner conductor from the distalend toward the proximal end, and the hollow portion may be defined by asubstantially concave surface within the inner conductor. In a furtherembodiment, the system may further include a coolant supply, and acoolant delivery system in communication with the coolant supply, wherethe coolant delivery system is operable to deliver a micro-controlledpulse of coolant to the distal end. In this further embodiment, theinner conductor may include at least one coolant delivery openingcoupled to the coolant delivery system, where the at least one coolantdelivery opening is configured to deliver coolant toward the distal end.The at least one coolant delivery opening may include at least oneinterior coolant delivery opening configured to deliver coolant throughthe opening and/or at least one exterior coolant delivery openingconfigured to deliver coolant outside of the periphery of the innerconductor.

Operation of embodiments according to the present invention may includepositioning an electrical energy conducting element at a surface of aneye and applying a selected amount of electrical energy through theelectrical energy conducting element to the eye. The energy conductingelement extends from a proximal end to a distal end, and the energyconducting element is operably connected to an electrical energy sourceat the proximal end. The selected amount of electrical energy is appliedaccording to a power parameter and a time parameter that generatestructural changes in a localized volume in the eye. The selected amountof electrical energy is deliverable according to a range of power valuesand a range of corresponding time values. The power parameter may be anupper power value in the range of power values, and the time parameteris a lower time value in the range of time values. The upper power valuemay be in a range of approximately 300 W to approximately 500 W. Theselected amount of electrical energy may be in a range of approximately2 J to approximately 25 J. The localized volume may be in a range ofapproximately 0.1 mm³ to approximately 2.0 mm³.

Another operation of embodiments according to present invention mayinclude positioning an energy conducting element to the eye and applyinga selected amount of electrical energy through the electrical energyconducting element to the eye according to a power parameter and a timeparameter. The energy conducting element, extending from a proximal endto a distal end, is operably connected to an electrical energy source atthe proximal end and is configured to deliver electrical energy togenerate a structural changes in a eye positioned at the distal end. Inthis method, the power parameter is greater than a threshold valuedetermining structural changes in a localized volume in the eye, and thetime parameter is less than a value of approximately 100 ms. Theselected amount of electrical energy may be a range of approximately 2 Jto approximately 25 J. The localized volume may have a value ofapproximately 0.1 mm³ to approximately 2.0 mm³.

Yet another embodiment includes an optical energy source, an opticalenergy conducting element, a coolant supply, and at least one coolantdelivery element. The optical energy conducting element, which isconnected to the optical energy source, extends from a proximal end to adistal end and directs optical energy from the optical energy source tothe distal end, which is positionable at an eye. The coolant deliveryelements are in communication with the coolant supply and are operableto deliver a micro-controlled pulse of coolant to the distal end.

An additional embodiment includes an energy source, a monopoleconductor, a coolant supply, and at least one coolant delivery element.The monopole conductor, which is connected to the energy source, extendsfrom a proximal end to a distal end and contacts, at the distal end, aneye of a body, whereby the body acts as a backplane and the conductordelivers energy to the eye. The coolant delivery elements are incommunication with the coolant supply and are operable to deliver amicro-controlled pulse of coolant to the distal end.

A further embodiment includes an energy source, a conducting element, acoolant supply, and a vacuum source. The conducting element, which isoperably connected to the energy source, extends from a proximal end toa distal end and directs energy from the energy source to the distalend, which is positionable at the eye. The vacuum source is operable todraw the coolant in a micro-controlled pulse from the coolant supply tothe distal end, whereby the pulse of coolant is applied to the eye.

In addition to delivering micro-controlled pulses of coolant, someembodiments may deliver pulses of energy. In particular, the embodimentsmay employ high power energy to generate heat in a targeted region ofthe eye in a relatively short amount of time. To minimize unwanteddiffusion of heat, the duration of the energy pulse may be shorter thanthe thermal diffusion time in the targeted region of the eye. In anexemplary application: a first pulse of coolant is delivered to reducethe temperature of the corneal surface; a high power pulse of microwaveenergy is then applied to generate heat within selected areas ofcollagen fibers in a mid-depth region; and a second pulse of coolant isdelivered in sequence to end further heating effect and “set” thecorneal changes that are caused by the energy pulse.

Another embodiment includes an energy conducting element and a vacuumring. The vacuum ring receives the energy conducting element and createsa vacuum connection with an eye and positions the energy conductingelement relative to the eye, whereby the energy conducting elementdirects the energy to the eye. The energy conducting element may bedetachably coupled to the vacuum ring.

The embodiments of the present invention may also employ a controller tocontrol the operation of one or more components or sub-systems. Inaddition, embodiments may employ pressure relief mechanisms to reducethe pressure introduced by the pulses of coolant into a closedenvironment. Furthermore, embodiments may also employ a readable useindicator, such as a radio frequency identification (RFID) device, thatensures that elements of the system, particularly those that come intocontact with the body and bodily fluids, are disposed of after one use.

These and other aspects of the present invention will become moreapparent from the following detailed description of the preferredembodiments of the present invention when viewed in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic of an embodiment of the presentinvention.

FIG. 2 illustrates an embodiment of the present invention employing amicrowave energy source.

FIG. 3A illustrates a variation of the embodiment of FIG. 2, whichemploys a pressure relief valve in place of a vacuum sub-system toreduce pressure created by a pulse of coolant.

FIG. 3B illustrates a variation of the embodiment of FIG. 2, whichemploys a vent passage in place of a vacuum sub-system to reducepressure created by a pulse of coolant.

FIG. 4 illustrates an embodiment of the present invention employing anoptical energy source.

FIG. 5A illustrates a variation of the embodiment of FIG. 4, whichemploys a pressure relief valve in place of a vacuum sub-system toreduce pressure created by a pulse of coolant.

FIG. 5B illustrates a variation of the embodiment of FIG. 4, whichemploys a vent passage in place of a vacuum sub-system to reducepressure created by a pulse of coolant.

FIG. 6 illustrates an embodiment of the present invention employing amonopole conductor as an energy conducting element.

FIG. 7A illustrates an embodiment of the present invention employing avacuum ring to position an applicator over an eye surface.

FIG. 7B illustrates the vacuum ring employed in the embodiment of FIG.7A.

FIG. 8A illustrates another embodiment of the present inventionemploying a microwave energy source.

FIG. 8B illustrates the inner conductor of the embodiment of FIG. 8A.

FIG. 8C illustrates the thin contact area for the inner conductor of theembodiment of FIG. 8A.

FIG. 8D illustrates the cooling delivery system in the inner conductorof the embodiment of FIG. 8A.

FIG. 8E illustrates the contact between an eye and the thin contact areafor the inner conductor of the embodiment of FIG. 8A.

FIG. 8F illustrates an example result of applying the applicator of theembodiment of FIG. 8A to an eye.

FIG. 9A illustrates a graph of change in energy required as a functionof increasing power for a constant target lesion size for a set ofsimulations employing the embodiment of FIG. 8A.

FIG. 9B illustrates a graph of maximum temperature reached as a functionof increasing power at a constant energy value for a set of simulationsemploying the embodiment of FIG. 8A.

FIG. 9C illustrates a graph of lesion volume as a function of increasingpower at a constant energy value for a set of simulations employing theembodiment of FIG. 8A.

DETAILED DESCRIPTION

Referring to FIG. 1, an embodiment of the present invention isschematically illustrated. In particular, FIG. 1 shows an applicator 10operably connected to an energy source 20. The applicator 10 includes anenergy conducting element 11, which extends from the proximal end 10A tothe distal end 10B of the applicator 10. The applicator 10 may beconnected to the energy source 20 at the proximal end 10A. Operation ofthe energy source 20 causes energy to be conducted through the energyconducting element 20 and heat to be generated at the distal end 10B. Assuch, the applicator 10 may be employed to apply heat to a cornea 2 ofan eye 1 that is positioned at or near the distal end 10B. Inparticular, the heat is applied to selected areas of collagen fibers ina mid-depth region 2B of the cornea 2 to shrink the collagen fibersaccording to a predetermined pattern and reshape the cornea 2, therebyimproving vision through the eye 1.

As further illustrated in FIG. 1, the applicator 10 includes at leastone coolant delivery element 12 in fluid communication with a coolantsupply, or reservoir, 13. The outer surface 10C of the applicator 10 maydefine a substantially enclosed assembly, especially when the distal end10B is placed in contact with the corneal surface 2A. As shown in FIG.1, this enclosed assembly may house the energy conducting element 11,the coolant delivery element 12, and the coolant supply 13. Although thecoolant supply 13 in FIG. 1 is positioned within the applicator 10, thecoolant supply 13 may be external to the applicator 10 in otherembodiments. Moreover, although FIG. 1 shows one coolant deliveryelement 12, some embodiments may employ more than one coolant deliveryelement 12 and/or more than one coolant supply 13.

The coolant delivery element 12 delivers a coolant, or cryogen, from thecoolant supply 13 to the distal end 10B of the applicator 10. As such,the applicator 10 may be employed to apply coolant to selectively coolthe surface 2A of the cornea 2 positioned at the distal end 10B. Thedelivery of coolant from the coolant delivery element 12 toward thecorneal surface 2A, in sequence with the application of heat to thecornea 2, permits the corneal temperature to be increased to causeappropriate shrinkage of the collagen fibers in the targeted mid-depthregion 2B and reshape the cornea 2, while also minimizing injury to theouter layer 2A, i.e. the epithelium, of the cornea 2.

A controller 40, as also shown in FIG. 1, may be operably connected tothe energy source 20 and/or the coolant delivery element 12. Thecontroller 40 may be employed to control the delivery of energy from theenergy source 20 to the applicator 10, thereby determining the magnitudeand timing of heat delivered to the cornea 2 positioned at the distalend 10B. In addition, the controller 40 may be employed to determine theamount and timing of coolant delivered from the coolant delivery element12 toward the corneal surface 2A at the distal end 10B. As describedfurther below, the controller 40 may be employed to selectively applythe heat and the coolant any number of times according to apredetermined or calculated sequence. For instance, the coolant may beapplied to the corneal surface 2A before, during, or after theapplication of heat to the cornea 2, or any combination thereof.

In some embodiments, the coolant delivery element 12 may employ adelivery nozzle 12A and a solenoid valve. The delivery nozzle 12A has anopening 12B directed at the distal end 10B. As is known, a solenoidvalve is an electromechanical valve for use with liquid or gascontrolled by applying or stopping an electrical current through a coilof wire, thus changing the state of the valve. As such, the controller40 may electronically control the actuation of the solenoid valve todeliver the coolant through the delivery nozzle 12A to the cornealsurface 2A. However, other embodiments may employ other types ofactuators or alternative techniques for delivering coolant through thedelivery nozzle 12A in place of a solenoid valve.

During operation of the embodiment of FIG. 1, the controller 40 may beused to actuate the application of micro-controlled pulses of coolant tothe corneal surface 2A before the application of heat to the cornea 2. Apulse, or a spurt, of coolant is applied to the corneal surface 2A for apredetermined short period of time so that the cooling remains generallylocalized at the corneal surface 2A while the temperature of deepercorneal collagen fibers 2B remains substantially unchanged. Preferably,the pulse is on the order of tens of milliseconds and is less than 100milliseconds. The delivery of the coolant to the corneal surface iscontrolled by the controller 40 and may be less than 1 millisecond.Furthermore, the time between the application of the coolant and theapplication of the heat is also controlled by the controller 40 and mayalso be less than 1 millisecond. The coolant pulse generally covers anarea of the corneal surface 2A that corresponds with the application ofheat to the cornea 2. The shape, size and disposition of the cooledregion may be varied according to the application.

Advantageously, localized delivery of coolant to the corneal surface 2Abefore the application of heat to the cornea 2 minimizes the resultingtemperature at the corneal surface 2A when the heat is applied, therebyminimizing any heat-induced injury to the corneal surface 2A. In otherwords, the coolant reduces the temperature of the corneal surface 2A, sothat the maximum surface temperature achieved at the corneal surface 2Aduring or immediately after heat exposure is also reduced by a similarmagnitude when compared to a case where no coolant is applied prior toheat exposure. Without the application of coolant, the temperature atthe corneal surface 2A rises during or immediately after heat exposurewith persistent surface heating resulting from a slow dissipation ofheat trapped near the surface-air interface.

Although temperatures observed at the corneal surface 2A immediatelyafter heat exposure are lowered by the application of coolant beforeexposure, a delayed thermal wave may arrive at the corneal surface 2Aafter exposure as the heat generated in the corneal areas 2B below thesurface 2A diffuses toward the cooled surface 2A. The heat transfer fromthe corneal surface 2A to the surrounding air is likely to beinsignificant, because air is an excellent thermal insulator. With nocooling after the application of heat, heat diffusing away from theareas 2B beneath the corneal surface 2A builds up near the cornealsurface 2A and produces an elevated surface temperature that may persistafter the application of heat. Although the heat that builds up near thecorneal surface 2A may eventually dissipate through thermal diffusionand cooling via blood perfusion, such dissipation may take severalseconds. More immediate removal of this heat by additional applicationof coolant minimizes the chances for heat-related injury to the cornealsurface 2A. Thus, embodiments of the present invention may employ notonly a pulse of coolant immediately prior to heat exposure, but also oneor more pulses of coolant thereafter. Accordingly, in further operationof the embodiment of FIG. 1, the controller 40 may also be used to applymicro-controlled pulses of coolant during or after the applicator 10applies heat to the cornea 2, or any combination thereof. Thisapplication of coolant rapidly removes heat which diffuses from themid-depth corneal region 2B to the corneal surface 2A.

When the coolant delivery element 12 delivers the pulse of coolant tothe corneal surface 2A, the coolant on the corneal surface 2A draws heatfrom the surface 2A, causing the coolant to evaporate. In general,coolant applied to the surface 2A creates a heat sink at the surface 2A,resulting in the removal of heat before, during, and after theapplication of heat to the cornea 2. The heat sink persists for as longas the liquid cryogen remains on the surface 2A. The heat sink canrapidly remove the trapped heat at the surface 2A without cooling thecollagen fibers in the region 2B. A factor in drawing heat out of thecornea 2 is the temperature gradient that is established near thesurface 2A. The steeper the gradient, the faster a given quantity ofheat is withdrawn. Thus, the application of the coolant attempts toproduce a large surface temperature drop as quickly as possible.

Because the cooled surface 2A provides a heat sink, the amount andduration of coolant applied to the corneal surface 2A affects the amountof heat that passes into and remains in the region underlying thecorneal surface 2A. Thus, controlling the amount and duration of thecooling provides a way to control the depth of corneal heating,promoting sufficient heating of targeted collagen fibers in themid-depth region 2B while minimizing the application of heat to regionsoutside the targeted collagen fibers.

In general, dynamic cooling of the corneal surface 2A may be optimizedby controlling: (1) the duration of the cooling pulse(s); (2) the dutycycle of multiple pulses; (3) the quantity of coolant deposited on thecorneal surface 2A so that the effect of evaporative cooling can bemaximized; and (4) timing of dynamic cooling relative to heatapplication. For example, a single pulse timing may include applying a80 ms heat pulse and a 40 ms cooling pulse at the beginning, middle, orend of the heating pulse. In another example, multiple cooling pulsesmay be applied according to a pattern of 10 ms ON and 10 ms OFF, withfour of these pulses giving a total of 40 ms of cooling, but timeddifferently.

In some embodiments, the coolant may be the cryogen tetrafluoroethane,C₂H₂F₄, which has a boiling point of about −26.5° C. and which is anenvironmentally compatible, nontoxic, nonflammable freon substitute. Thecryogenic pulse released from the coolant delivery element 12 mayinclude droplets of the cryogen cooled by evaporation as well as mistformed by adiabatic expansion of vapor.

In general, the coolant may be selected so that it provides one or moreof the following: (1) sufficient adhesion to maintain good surfacecontact with the corneal surface 2A; (2) a high thermal conductivity sothe corneal surface 2A may be cooled very rapidly prior to heatapplication; (3) a low boiling point to establish a large temperaturegradient at the surface; (4) a high latent heat of vaporization tosustain evaporative cooling of the conical surface 2A; and (5) noadverse health or environmental effects. Although the use oftetrafluoroethane may satisfy the criteria above, it is understood thatembodiments of the present invention are not limited to a particularcryogen and that other coolants, such as liquid nitrogen, argon, or thelike, may be employed to achieve similar results. For instance, in someembodiments, other liquid coolants with a boiling temperature of belowapproximately body temperature, 37° C., may be employed. Furthermore,the coolant does not have to be a liquid, but in some embodiments, mayhave a gas form. As such, the pulse of coolant may be a pulse of coolinggas. For example, the coolant may be nitrogen (N₂) gas or carbon dioxide(CO₂) gas.

Referring now to the cross-sectional view illustrated in FIG. 2, anembodiment of the present invention employs an applicator 110. Theapplicator 110 includes an electrical energy conducting element 111, amicro-controlled coolant delivery system 112, as well as a coolantsupply 113.

The electrical energy conducting element 111 is operably connected to anelectrical energy source 120, for example, via conventional conductingcables. The electrical energy conducting element 111 extends from aproximal end 110A to a distal end 110B of the applicator 110. Theelectrical energy conducting element 111 conducts electrical energy fromthe source 120 to the distal end 110B to apply heat energy to a cornea2, which is positioned at the distal end 110B. In particular, theelectrical energy source 120 may include a microwave oscillator forgenerating microwave energy. For example, the oscillator may operate ata microwave frequency range of 400 MHz to 3000 MHz, and morespecifically at a frequency of around 915 or around 2450 MHz which hasbeen safely used in other applications. As used herein, the term“microwave” corresponds to a frequency range from about 10 MHz to about10 GHz.

As further illustrated in FIG. 2, the electrical energy conductingelement 111 may include two microwave conductors 111A and 111B, whichextend from the proximal end 110A to the distal end 110B of theapplicator 110. In particular, the conductor 111A may be a substantiallycylindrical outer conductor, while the conductor 111B may be asubstantially cylindrical inner conductor that extends through an innerpassage extending through the conductor 111A. With the inner passage,the conductor 111A has a substantially tubular shape. The inner and theouter conductors 111A and 111B may be formed, for example, of aluminum,stainless steel, brass, copper, other metals, coated metals,metal-coated plastic, or any other suitable conductive material.

With the concentric arrangement of conductors 111A and 111B, asubstantially annular gap 111C of a selected distance is defined betweenthe conductors 111A and 111B. The annular gap 111C extends from theproximal end 110A to the distal end 110B. A dielectric material 111D maybe used in portions of the annular gap 111C to separate the conductors111A and 111B. The distance of the annular gap 111C between conductors111A and 111B determines the penetration depth of microwave energy intothe cornea 2 according to established microwave field theory. Thus, themicrowave conducting element 111 receives, at the proximal end 110A, theelectrical energy generated by the electrical energy source 120, anddirects microwave energy to the distal end 111B, where the cornea 2 ispositioned.

The outer diameter of the inner conductor 111B is preferably larger thanthe pupil. In general, the outer diameter of the inner conductor 111Bmay be selected to achieve an appropriate change in corneal shape, i.e.keratometry, induced by the exposure to microwave energy. Meanwhile, theinner diameter of the outer conductor 111A may be selected to achieve adesired gap between the conductors 111A and 111B. For example, the outerdiameter of the inner conductor 111B ranges from about 2 mm to about 10mm while the inner diameter of the outer conductor 111A ranges fromabout 2.1 mm to about 12 mm. In some embodiments, the annular gap 111Cmay be sufficiently small, e.g., in a range of about 0.1 mm to about 2.0mm, to minimize exposure of the endothelial layer of the cornea(posterior surface) to elevated temperatures during the application ofheat by the applicator 110.

As shown in FIG. 2, the micro-controlled coolant delivery system 112 aswell as the coolant supply 113 may be positioned within the annular gap111C. Although FIG. 2 may illustrate one coolant delivery system 112,the applicator 110 may include a plurality of coolant delivery systems112 arranged circumferentially within the annular gap 111C. The coolantsupply 113 may be an annular container that fits within the annular gap111C, with the coolant delivery element 112 having a nozzle structure112A extending downwardly from the coolant supply 113 and an opening112B directed toward the distal end 110B.

The micro-controlled coolant delivery system 112, which is in fluidcommunication with the coolant supply 113, may operate in a mannersimilar to the coolant delivery system 12 in FIG. 1. In other words,pulses of coolant, or cryogen, from the coolant supply 113 arepreferably applied to the corneal surface 2A before, during, and afterenergy is applied to the cornea 2 with the electrical energy source 120and the electrical energy conducting element 111.

As described previously, the controller 140 may be employed toselectively apply the heat and the coolant pulses any number of timesaccording to any predetermined or calculated sequence. In addition, theheat and the pulses of coolant may be applied for any length of time.Furthermore, the magnitude of heat being applied may also be varied.Adjusting such parameters for the application of heat and pulses ofcoolant determines the extent of changes that are brought about withinthe cornea 2. Of course, as discussed, embodiments of the presentinvention attempt to limit the changes in the cornea 2 to an appropriateamount of shrinkage of selected collagen fibers. When employingmicrowave energy to generate heat in the cornea 2, for example with theapplicator 110, the microwave energy may be applied with low power (ofthe order of 40 W) and in long pulse lengths (of the order of onesecond). However, other embodiments may apply the microwave energy inshort pulses. In particular, it may be advantageous to apply themicrowave energy with durations that are shorter than the thermaldiffusion time in the cornea. For example, the microwave energy may beapplied in pulses having a higher power in the range of 300 W to 3 kWand a pulse duration in the range of about 10 milliseconds to about onesecond. Thus, when applying the coolant pulses before and after theapplication of heat as discussed previously: a first pulse of coolant isdelivered to reduce the temperature of the corneal surface 2A; a highpower pulse of microwave energy is then applied to generate heat withinselected areas of collagen fibers in a mid-depth region 2B; and a secondpulse of coolant is delivered in sequence to end further heating effectand “set” the corneal changes that are caused by the energy pulse. Theapplication of energy pulses and coolant pulses in this manneradvantageously reduces the amount to heat diffusion that occurs andminimizes the unwanted impact of heating and resulting healing processeson other eye structures, such as the corneal endothelium. Moreover, thistechnique promotes more permanent and stable change of the shape of thecornea 2 produced by the heat. Although the application of high poweredenergy in short pulses has been described with respect to the deliveryof microwave energy, a similar technique may be applied with other typesof energy, such as optical energy or electrical energy with radiofrequency (RF) wavelengths described further below.

Referring again to FIG. 2, at least a portion of each of the conductors111A and 111B may be covered with an electrical insulator to minimizethe concentration of electrical current in the area of contact betweenthe corneal surface 2A and the conductors 111A and 111B. In someembodiments, the conductors 111A and 111B, or at least a portionthereof, may be coated with a material that can function both as anelectrical insulator as well as a thermal conductor. A dielectric layer110D may be employed along the distal end 111B of the applicator 110 toprotect the cornea 2 from electrical conduction current that wouldotherwise flow into the cornea 2 via conductors 111A and 111B. Suchcurrent flow may cause unwanted temperature effects in the cornea 2 andinterfere with achieving a maximum temperature within the collagenfibers in the mid-depth region 2B of the cornea 2. Accordingly, thedielectric layer 110D is positioned between the conductors 111A and 111Band the cornea 2. The dielectric layer 110D may be sufficiently thin tominimize interference with microwave emissions and thick enough toprevent superficial deposition of electrical energy by flow ofconduction current. For example, the dielectric layer 110D may be abiocompatible material, such as Teflon, deposited to a thickness ofabout 50 μm. In general, an interposing layer, such as the dielectriclayer 110D, may be employed between the conductors 111A and 111B and thecornea 2 as long as the interposing layer does not substantiallyinterfere with the strength and penetration of the microwave radiationfield in the cornea 2 and does not prevent sufficient penetration of themicrowave field and generation of a desired heating pattern in thecornea 2. The dielectric material may be elastic, such as polyurethaneand silastic, or nonelastic, such as Teflon and polyimides. Thedielectric material may have a fixed dielectric constant or varyingdielectric constant by mixing materials or doping the sheet, thevariable dielectric being spatially distributed so that it may affectthe microwave hearing pattern in a customized way. The thermalconductivity of the material may have fixed thermal properties (thermalconductivity or specific heat), or may also vary spatially, throughmixing of materials or doping, and thus provide a means to alter theheating pattern in a prescribed manner. Another approach for spatiallychanging the heating pattern is to make the dielectric sheet material ofvariable thickness. The thicker region will heat less than the thinnerregion and provides a further means of spatial distribution of microwaveheating.

During operation, the distal end 110B of the applicator 110 as shown inFIG. 2 is positioned on or near the corneal surface 2A. Preferably, theapplicator 110 makes direct contact with the corneal surface 2A. Inparticular, such direct contact positions the conductors 111A and 111Bat the corneal surface 2A (or substantially near the corneal surface 2Aif there is a thin interposing layer between the conductors 111A and111B and the corneal surface 2A). Accordingly, direct contact helpsensure that the pattern of microwave heating in the corneal tissue hassubstantially the same shape and dimension as the gap 111C between thetwo microwave conductors 111A and 111B. An annulus is a preferredheating pattern because the inner diameter of the heated annulus can beselected to be sufficiently large so as to avoid heating the centralcornea overlying the pupil.

The advantages of direct contact between the applicator 110 and thecorneal surface 2A may be reduced by the presence of a layer of fluidcoolant which may exist therebetween. Rather than creating an annularheating pattern with dimensions equal to that of the gap between theconductors 111A and 111B, the presence of such a fluid layer may cause aless desirable circle-shaped microwave heating pattern in the cornea 2with a diameter less than that of the inner conductor 111B. Therefore,embodiments of the present invention do not require a flow of coolant ora cooling layer to exist over the corneal surface 2A during theapplication of energy to the cornea 2. In particular, the short pulsesfrom the coolant delivery element 112 may apply a coolant thatevaporates from the corneal surface before the application of themicrowave energy and thus does not create a fluid layer that wouldinterfere with the desired microwave pattern.

Embodiments may employ a vacuum passageway 114 operably connected to avacuum source 130. The vacuum passageway 114 may have an opening 114Athat is positioned near the corneal surface 2A and opens to the interiorof the applicator 110. The vacuum source 130 may be used to draw anycoolant, or unwanted fluid layer, from the corneal surface 2A before themicrowave energy is applied to the cornea 2. In this case, the vacuumsource 130 also draws the fluid to a waste receptacle (not shown).

The application of coolant and the subsequent evaporation of coolant maycause the pressure to increase within the applicator 110. In particular,the applicator 110 may have an outer surface 110C that may define asubstantially enclosed assembly, especially when the distal end 110B isplaced in contact with the corneal surface 2A. As shown in FIG. 2, thesubstantially enclosed assembly contains the electrical conductingelement 111, the coolant delivery element 112, the coolant supply 113,as well as the vacuum passageway 114. The pressure is more likely toincrease within such an enclosed assembly. As the applicator 110 may bein contact with the corneal surface 2A, the resulting pressure may actagainst the corneal surface 2A. Therefore, to minimize the effects ofthis pressure on the corneal surface 2A, embodiments may employ apressure relief mechanism for removing excess pressure that may occur inthe applicator 110.

In addition to the functions of the vacuum passageway 114 discussedpreviously, the vacuum passageway 114 with opening 114A may also act asa pressure relief mechanism for the applicator 110. As such, thepressure in the applicator 110 may be lowered by activating the vacuumsource 130. Alternatively, as shown in FIG. 3A, the applicator 110 mayinclude any type of pressure relief valve 118 that opens up the interiorof the applicator 110 to the environment external to the applicator 110when the pressure in the applicator 110 rises to a certain level. Asanother alternative shown in FIG. 3B, the applicator 110 may simplyemploy a vent passage 119 that places the interior of the applicator 110in communication with the environment external to the applicator 110, inwhich case the pressure interior will generally be in equilibrium withthe external area.

As FIG. 2 further illustrates, the vacuum passageway 114 also passesthrough the dielectric material 110D and has an opening 114B at thedistal end 110B. While the opening 114A opens to the interior of theapplicator 110, the opening 114B opens to the corneal surface 2A whichis positioned at the distal end 110B. With the opening 114B positionedat the corneal surface 2A, the vacuum passageway 114 with the vacuumsource 140 helps the applicator 110 to maintain a fixed positionrelative to cornea 2 during treatment. The vacuum source 130 may apply acontrolled amount of suction to the corneal surface 2A to ensure thatthe applicator surface at the distal end 110B has a firm and evencontact with the cornea 2.

Referring to FIG. 8A, an alternative embodiment employs an applicator510, which includes an electrical energy conducting element 511, amicro-controlled coolant delivery system 512, as well as a coolantsupply 513. Except where indicated otherwise, the applicator 510 may besimilar in many respects to the applicator 110. In general, theelectrical energy conducting element 510 extends from a proximal end510A to a distal end 510B of the applicator 510. The electrical energyconducting element 511 is operably connected to an electrical energysource 520 at the proximal end 510A and conducts electrical energy tothe distal end 510B to apply energy, for example, to a cornea 2 of aneye 1. For example, the electrical energy source 520 may include amicrowave oscillator for generating microwave energy.

As shown in FIG. 8A, the electrical energy conducting element 511includes electrodes 511A and 511B, which extend from the proximal end510A to the distal end 510B of the applicator 510. In particular, theelectrode 511A is an outer conductor with an inner passage, while theelectrode 511B is an inner conductor that extends through the innerpassage of the conductor 511A. The inner and the outer conductors 511Aand 511B may be formed, for example, of aluminum, stainless steel,brass, copper, other metals, coated metals, metal-coated plastic, or anyother suitable conductive material.

The outer conductor 511A and the inner conductor 511B may besubstantially cylindrical at least at the distal end 510B. As such, theouter conductor 511A and the inner conductor 511B may be concentricallyarranged. With this concentric arrangement, a substantially annular gap511C of a selected distance may be defined between the conductors 511Aand 511B. The distance, or radial thickness, of the annular gap 511Cbetween conductors 511A and 511B determines the penetration depth ofmicrowave energy into the cornea 2 according to established microwavefield theory. Thus, the energy conducting element 511 receives, at theproximal end 510A, the electrical energy generated by the electricalenergy source 520, and directs microwave energy to the distal end 511B,where the cornea 2 is positioned.

The outer diameter of the inner conductor 511B is preferably larger thanthe pupil. In general, the outer diameter of the inner conductor 511Bmay be selected to achieve an appropriate change in corneal shape, i.e.keratometry, induced by the exposure to microwave energy. Meanwhile, theinner diameter of the outer conductor 511A may be selected to achieve adesired gap between the conductors 511A and 511B. For example, the outerdiameter of the inner conductor 511B may range from approximately 2 mmto approximately 10 mm while the inner diameter of the outer conductor111A ranges from approximately 2.1 mm to approximately 12 mm. In someembodiments, the annular gap 511C may be range from approximately 0.1 mmto approximately 2.0 mm, or preferably approximately 0.5 mm toapproximately 1.5 mm.

As shown further in FIG. 8A, the distal end 510B of the inner conductor511B includes a thin contact area 511E. In particular, the contact area511E may be a thin annular surface that is disposed along the peripheryof a substantially circular opening 51111 at the distal end 510B. Insome embodiments, the contact area 511E may have a radial thickness ofapproximately 50 μm to approximately 200 μm. The inner electrode 511B isshown in greater detail in FIGS. 8B-D. FIG. 8B illustrates a perspectiveview of the inner electrode 511B, while FIG. 8C shows a closer view ofthe contact area 511E. The circular opening 511H is defined by a hollowportion 511G that extends into the inner conductor 511B from the distalend 510B. The hollow portion 511G is defined, in turn, by a concave,substantially semi-spherical surface 5111 within the inner conductor511B. When the inner conductor 511B is applied to an eye, the interiorsurface 5111 is shaped so that only the thin contact area 511E contactsthe corneal surface 2A. Similar to embodiments discussed previously, adielectric layer may be employed along the contact area 511E.

As illustrated in FIG. 8A, the energy conducting element 511 may includeat least one vent 519 that helps to control the pressure within thehollow portion 511G. For example, an interior vent 519 may connect thehollow portion 511G to the gap 511C between the inner electrode and theouter electrode, and an exterior vent may connect the gap 511C to anexterior area outside the energy conducting element 511.

FIG. 8E illustrates the thin contact area 511E positioned at the cornealsurface 2A of an eye 1. In addition, FIG. 8F shows a ring 3 thatcorresponds to the uniform shrinkage of corneal fibers resulting fromthe application of energy via the thin contact area 511E (with a radialthickness of approximately 200 μm) to the corneal surface 2A. As shownin FIG. 8F, employing a thin contact area 511E produces a well-definedcontact area with the corneal surface 2A, leading to uniform circularcontact. In particular, the narrow contact between the inner electrode511B and the corneal surface 2A results in a very localized microwavecontact area and power deposition region. Moreover, the small thermalmass corresponding to the inner electrode 511B enables more controlledcooling. Although the contact area 511E shown in FIGS. 8A-D may besubstantially annular, it is contemplated that other embodiments mayemploy contact areas of other shapes, such as an ellipse, that deliverenergy to the cornea 2 according to a well-defined pattern.

As further illustrated in FIGS. 8B-C, the inner conductor 511B mayinclude openings, or ports, 512C, D, E for delivering coolant from thecoolant source 513 to the eye 1 positioned at the distal end 510B. Theopenings 512C, D are disposed within the hollow portion 511G, while theopenings 512E are disposed along an exterior surface 511J of the innerconductor 511B. Accordingly, as shown in FIG. 8A, the openings 512C, Ddeliver coolant to the eye 1 from the interior of the inner conductor511B, and the openings 512E deliver coolant to the eye 1 from the gap511C, outside the inner conductor 511B.

Any number of openings 512C, D, E may be sized and arranged according toany configuration that achieves a predetermined delivery of coolant tothe eye 1. In the example of FIGS. 8B-C, the plurality of openings 512Eare equally spaced around the inner conductor 511B, while the pluralityof openings 512C, D are arranged in two concentric circles. Inparticular, the openings 512C are equally spaced in a larger circledisposed along the surface 5111, while the openings 512D are equallyspaced in a smaller circle along the angled surface of an interiorstructure 511K. The interior structure 511K, which is generallyfrustoconical, is disposed centrally within the hollow portion 511G.Positioning the smaller openings 512D on its angled surface allows thecoolant to be delivered at a particular angle to the eye 1. FIGS. 8B-Calso illustrate that openings 512C, D, E may have varying sizes todeliver a predetermined amount of coolant from each opening.

FIG. 8D shows the coolant delivery system 512 within the inner conductor511B. In particular, coolant channels 512A, B are operably connected tothe coolant source 513 and direct coolant through the openings 512C, D,E. A central channel 512A extends centrally through the inner conductor511B to the distal end 510B, and additional channels 512B branch out tothe openings 512C, D, E. The branching channels 512B may be angled withrespect to the interior surface 5111, the interior structure 511K, andthe exterior surface 511J so that the coolant passes through theopenings 512C, D, E at selected angles toward the eye 1.

As described previously, a controller 540, as shown in FIG. 8A, may beoperably connected to the energy source 520 and/or the coolant deliverysystem 512. The controller 540 may be employed to control the deliveryof energy from the energy source 520 to the applicator 510, therebydetermining the magnitude and timing of energy delivered to the cornea 2positioned at the distal end 510B. In addition, the controller 540 maybe employed to determine the amount and timing of coolant delivered fromthe coolant delivery element 512 toward the eye 1 at the distal end510B. In particular, the controller 540 may be employed to selectivelyapply the energy and the coolant any number of times according to apredetermined or calculated sequence. For instance, the coolant may beapplied to the corneal surface 2A before, during, and/or after theapplication of heat to the cornea 2.

During operation of the applicator 510, the electrical energy conductingelement 511 is positioned at a corneal surface 2A of an eye 1. Aselected amount of electrical energy is delivered through the thincontact area 511E to the cornea 2 according to a power parameter and atime parameter. The power parameter and the time parameter generatestructural changes in a localized volume in the eye.

Numerical modeling with a commercially available package (e.g., fromCOMSOL, Inc.) was performed in an eye model to compare a range of energysettings (power×time) and the resulting lesion, defined as the region ofcorneal shrinkage. The lesion is defined as the region in the eye thatattains a temperature of 65° C. due to the power and time applied withan energy conducting element 511 having a thin contact area 511E. Inthese simulations, the annular thickness of the thin contact area 511Ewas approximately 100 μm while the gap 511C between the electrodes wasapproximately 1.25 mm. A membrane of polyurethane with a thickness of 35μm was also placed between the thin contact area 511E and the cornealsurface. The initial temperature for the cornea, aqueous layer, lens andboth the outer conductor 511A and the inner conductor 511B was set to20° C.

In a first set of simulations, the application of the energy conductingelement 511 was compared for different power settings while maintainingsubstantially the same lesion size. Specifically, energy was varied bychanging the pulse time, and power was varied from 100 W to 500 W inincrements of 100 W, while the volume of the lesion size remainedsubstantially constant (with temperature remaining substantiallyconstant at 65° C.).

Results of Simulations Varying Energy and Power while Keeping LesionSize Constant

TABLE 1 Max Area Volume % Deviation Pow- Ener- temp of of in volume er/Time/ gy/ Reached/ ROI > ROI > compared to W ms J C. 65 C./m2 65 C./m3minimum 500 10.2 5.1 111.2 1.60E−08 2.48E−10 1.8% 400 13 5.2 106.61.59E−08 2.46E−10 1.2% 300 17.9 5.37 100.58 1.57E−08 2.43E−10 0.0% 20029 5.8 93.1 1.59E−08 2.46E−10 1.2% 100 75 7.5 82.5 1.58E−08 2.45E−100.7%

The results of the first set of simulations are provided in TABLE 1.TABLE 1 shows the range of power values and the range of time valuesrequired to achieve the constant target lesion size. At higher powers,less energy was required for the same lesion size. For example, when thepower applied was 100 W, the power was applied for 75 ms to produce 7.5J and to achieve the target lesion. When power was increased to 500 W,however, the power was applied for only 10.2 ms to produce 5.1 J andachieve the target lesion. FIG. 9A also provides a graph of change inenergy as a function of increasing power for a constant target lesionsize. Accordingly, as power increases, the energy requirements decreasefor the same tissue effect, i.e., a constant lesion size at 65° C.

A second set of simulations was also performed by calculating the lesionsize while keeping the energy level constant at 5 J and varying thepower. Time and power were adjusted at each power level to maintain 5 J.FIG. 9B shows the maximum temperature reached as a function ofincreasing power for the second set of simulations, while FIG. 9C showslesion volume as a function of increasing power. As shown by FIG. 9B,the maximum temperature increased as the power increased. As shown inFIG. 9B, the rate of change at low powers (between 100 W and 200 W) wasgreater than the rate at higher powers (200 W and 500 W). In particular,the maximum temperature increased by a factor of 1.23 times whendoubling power from 100 W to 200 W, and by a factor of 1.17 times whendoubling power from 200 W to 400 W. Correspondingly, as shown by FIG.9C, the lesion volume (defined as the region that achieved or exceeded65° C.) increased as the power increased. Similar to the graph of FIG.9B, the rate of change at low power (between 100 W and 200 W) was higherthan the rate at higher power (200 W and 500 W). In particular, thevolume increased by a factor of 2.9 times when doubling power from 100 Wto 200 W, and by a factor of 1.22 times when doubling power from 200 Wto 400 W.

Accordingly, the selected amount of electrical energy is deliverableaccording to a range of power values and a range of corresponding timevalues. To produce a selected lesion volume in a cornea, the range ofpower values must exceed a particular threshold power value and therange of time values be less than a particular threshold time value.Although a large amount of energy may be delivered to the cornea byapplying a low power value over a longer period of time, the desiredlesion may not be sufficiently generated in the corneal tissue with suchparameters. Indeed, as described above, a selected lesion volume may beproduced by applying less energy with a higher power. Thus, duringoperation of the applicator 511, the power parameter may be an upperpower value in the range of power values, while the corresponding timeparameter is a lower time value in the range of time values. Inparticular, the upper power value may range from approximately 300 W toapproximately 500 W, while the lower time value may range fromapproximately 4 ms to approximately 80 ms. Correspondingly, the selectedamount of energy applied to the eye 1 may range from approximately 2 Jto approximately 25 J. Moreover, the localized volume may fromapproximately 0.1 mm³ to approximately 2.0 mm³. Although powerparameters and time parameters for applying energy to an eye may bediscussed with reference to the embodiment of FIG. 8A, it is understoodthat power parameters and time parameters may be determined in a similarmanner for other embodiments.

Referring now to the cross-sectional view illustrated in FIG. 4, anotherembodiment of the present invention employs an applicator 210, whichincludes an optical energy conducting element 211, a micro-controlledcoolant delivery system 212, as well as a coolant supply 213.

The optical energy conducting element 211 is operably connected to anoptical energy source 220, for example, via conventional optical fiber.The optical energy source 220 may include a laser, a light emittingdiode, intense pulsed light (IPL), or the like. The optical energyconducting element 211 extends to the distal end 210B from the proximalend 210A, where it is operably connected with the optical source 220.The optical energy conducting element includes an optical fiber 211A.Thus, the optical fiber 211A receives optical energy from the opticalenergy source 220 at the proximal end 210A and directs the opticalenergy to the distal end 210B, where the cornea 2 of an eye 1 ispositioned. A controller 240 may be operably connected to the opticalenergy source 220 to control the delivery, e.g. timing, of the opticalenergy to the optical conducting element 211. The optical energyconducting element 211 irradiates the cornea 2 with the optical energyand generates heat for appropriately shrinking collagen fibers in themid-depth region 2B of the cornea 2. As also illustrated in FIG. 4, theoptical conducting element may optionally include an optical focuselement 212B, such as a lens, to focus the optical energy and todetermine the pattern of irradiation for the cornea 2.

As FIG. 4 illustrates, the coolant delivery system 212 may be positionedadjacent to the optical energy conducting element 211. The coolantdelivery system 212, which is in fluid communication with the coolantsupply 213, delivers micro-controlled pulses of coolant, or cryogen,from the coolant supply 213 to the corneal surface 2A. Such pulses ofcoolant may be applied before and/or after energy is applied to thecornea 2 with the optical energy source 220 and the optical energyconducting element 211.

FIG. 4 further illustrates another technique for delivering pulses ofcoolant to the corneal surface 2A. In particular, the pulse of coolantmay be drawn from the coolant delivery element 212 by creating an areaof low pressure at or near the distal end 210B, where the cornealsurface 2A is positioned. As shown in FIG. 4, the applicator 210 mayhave a vacuum passageway 214, such as a tube structure, which isconnected to the vacuum source 230. The vacuum passageway 214 has anopening 214A which is positioned at or near the distal end 210B tocreate the area of low pressure. To enhance the applicator's ability tocreate this low pressure area, the applicator 210, as illustrated inFIG. 4, may include a contact element 215 that defines a small enclosurein which the area of low pressure can be created.

In particular, FIG. 4 shows that the applicator 210 includes a contactelement 215 at the distal end 210B which makes contact with the cornealsurface 2A. The contact element 215 has a housing 215A with a cavity215B. The housing 215A has an opening 215C at the distal end 210B of theapplicator 210, so that the cavity 215B is exposed to the distal end210B. As such, the contact element 215 forms an enclosure over thecornea 2 when it is positioned over the cornea 2. As shown further inFIG. 4, the nozzle structure 212A of the coolant delivery element 212 isreceived by the contact element 215 and the opening 212B opens to thecavity 215B. In some embodiments, the coolant delivery system 212 simplyplaces the coolant supply in communication with the contact element 215via structure 212A. While one coolant delivery element 212 isillustrated in FIG. 4, it is understood that more than one coolantdelivery element 212 may be employed by the applicator 210. The vacuumpassageway 214 is also received by the contact element, where theopening 214A opens to the cavity 215B. Accordingly, when the contactelement 215 is positioned over the corneal surface 2A to form anenclosure, the vacuum source 240 may be operated to create a near vacuumor low pressure in the cavity 215B, which in turn draws the coolantthrough the nozzle structure 212A toward the corneal surface 2Apositioned at the opening 215C. The controller 240 may be operablyconnected to control the vacuum source 240 to cause micro-controlledpulses of coolant to be drawn from the coolant delivery element 212.

Of course, it is understood that in other embodiments, the contactelement 215 may be employed with a coolant delivery element 212 thatemploys a solenoid valve, or other actuator, and does not require thevacuum source 230. As such, the controller 140 may electronicallycontrol the solenoid valve, or other actuator, to deliver the coolant tothe corneal surface 2A.

The application of coolant to the corneal surface 2A and the subsequentevaporation of coolant may cause the pressure to increase within thecavity 215A of the contact element 215. As the contact element 215 ispositioned against the corneal surface 2A, the resulting pressure mayact against the corneal surface 2A. Therefore, to minimize the effectsof this pressure on the corneal surface 2A, embodiments may employ apressure relief mechanism for removing excess pressure that may occur inthe applicator 210.

In addition to providing a way to initiate micro-controlled pulses ofcoolant, the vacuum passageway 214 may also act as a pressure reliefmechanism for the applicator 210. As such, the pressure in theapplicator 210 may be lowered by activating the vacuum source 230.Alternatively, as shown in FIG. 5A, the applicator 210 may include anytype of pressure relief valve 218 that opens up the interior of theapplicator 210 to the environment external to the applicator 210 whenthe pressure in the applicator 210 rises to a certain level. As anotheralternative shown in FIG. 5B, the applicator 210 may simply employ avent passage 219 that places the interior of the applicator 210 incommunication with the environment external to the applicator 210, inwhich case the interior pressure will generally be in equilibrium withthe external area. Of course, as there is no vacuum source shown in theembodiments of FIGS. 5A and 5B, the coolant delivery element 212requires another element such as a solenoid valve, or other actuator, todeliver the pulses of coolant.

As further shown in FIG. 4, the contact element 215 also receives theoptical conducting element 211, so that the applicator 210 can deliverthe optical energy from the optical energy source 220 to the cornea 2 atthe distal end 210B. FIG. 4 shows that the optical focus element 211B isconnected to the contact element 215.

Advantageously, the contact element 215 may act as an additional heatsink for drawing heat from the corneal surface 2A, as the contactelement 215 is in direct contact with the corneal surface 2A. Inparticular, the contact element may be formed from a heat conductingmaterial, such as a metal. In general, other heat sinks, such as metalapplicator walls 410C, may be employed with embodiments of the presentinvention to provide further heat transfer from the corneal surface 2A.

As FIG. 4 further illustrates, the vacuum passageway 214 also has anopening 214B at the distal end 210B. While the opening 214A opens to thecavity 215B of the contact element 215, the opening 214B opens to thecorneal surface 2A which is positioned at the distal end 110B. With theopening 214B positioned at the corneal surface 2A, the vacuum passageway214 with the vacuum source 240 helps the applicator 210 to maintain afixed position relative to cornea 2 during treatment. The vacuum source230 may apply a controlled amount of suction via opening 214B to thecorneal surface 2A to ensure that applicator surface at the distal end210B has a firm and even contact with the cornea 2.

Referring now to the cross-sectional view illustrated in FIG. 6, anotherembodiment of the present invention is illustrated. In particular, theembodiment of FIG. 6 illustrates an applicator 310 which employs amonopole conducting element 311 for conducting energy to the cornea 2.

The monopole conducting element 311 is operably connected to anelectrical energy source 320, which may provide a radio frequency (RF)electrical energy. The monopole 311 extends to the distal end 310B fromthe proximal end 310A, where it is operably connected with theelectrical energy source 320. The monopole conducting element 311 mayhave a needle-like shape at the distal end 310B, which is designed tocontact or penetrate the cornea 2. When the applicator is positioned toplace the monopole 311 into contact with the eye 1, the body in contactwith the applicator 310 acts as a backplane to complete the circuit.Accordingly, the monopole 311 may receive the electrical energygenerated at the electrical energy source 320 and conduct electricalenergy to the cornea 2 of an eye 1. As a result, heat is generatedwithin the cornea 2 to shrink selected collagen fibers in the mid-depthregion 2B of the cornea 2 and to reshape the cornea 2. A controller 340may be operably connected to the electrical energy source 320 to controlthe delivery, e.g. timing, of the electrical energy to the monopole 311.

Other aspects of the embodiment of FIG. 6 are similar to the embodimentsdescribed previously. In particular, as FIG. 6 illustrates, theapplicator 310 also employs a micro-controlled coolant delivery system312 as well as a coolant supply 313. The micro-controlled coolantdelivery system 312 is positioned adjacent to the monopole 311. Thecoolant delivery element 312 may employ a nozzle structure 312A with anopening 312B directed at the distal end 310B. A solenoid valve, or otheractuator, may be employed to create the pulses of coolant. Thecontroller 340 may electronically control the solenoid valve, or otheractuator, to deliver the coolant to the corneal surface 2A. As such, themicro-controlled coolant delivery system 312, which is in fluidcommunication with the coolant supply 313, operates in a manner similarto the coolant delivery system 12 in FIG. 1. In other words, pulses ofcoolant, or cryogen, from the coolant supply 313 are preferably appliedto the corneal surface 2A before, during, or after the energy is appliedto the cornea 2, or any combination thereof.

As also shown in FIG. 6, the applicator 320 may include a vacuumpassageway 314 with an opening 314A positioned at or near the distal end310B. The vacuum passageway 314 is operably connected to a vacuum source330, which may be controlled by the controller 340. Similar to otherembodiments described previously, the vacuum source 340 and the vacuumpassageway 314 may be operated to relieve pressure created by thedelivery of coolant from the coolant delivery element 312.Alternatively, a pressure relief valve or a vent passage may be employedto act as the pressure relief element, in a manner similar toembodiments described previously.

In addition, as further shown in FIG. 6, the vacuum passageway 314 mayalso have an opening 314B that opens to the corneal surface 2A which ispositioned at the distal end 310B. With the opening 314B positioned atthe corneal surface 2A, the vacuum passageway 314 with the vacuum source340 creates suction between the applicator 110 and the corneal surface2A to maintain the applicator 310 in a fixed position relative to cornea2 during treatment.

In general, any arrangement of vacuum openings operably connected to avacuum source may be employed to keep embodiments of the presentinvention in position over the corneal surface during treatment. Forexample, FIG. 7A shows an applicator 410 which is positioned over thecornea 2 with a vacuum ring 417. Like the applicators described above,the applicator 410 includes an energy conducting element 411, such asthose discussed previously, which extends from the proximal end 410A tothe distal end 410B of the applicator 410. The energy conducting element411 is operably connected to an energy source 420 at the proximal end410A. Operation of the energy source 420 causes energy to be conductedthrough the energy conducting element 420 and heat to be generated atthe distal end 410B. As such, the vacuum ring 417 positions the distalend 410B of the applicator 410 over the cornea 2 to enable the energyconducting element 411 to generate heat at the cornea 2. In particular,the heat is applied to targeted collagen fibers in a mid-depth region 2Bof the cornea 2, thereby shrinking the collagen fibers and reshaping thecornea 2 to improve vision through the eye 1.

As shown further in FIGS. 7A and 7B, the vacuum ring 417 has asubstantially annular structure and receives the energy conductingelement 411 coaxially through a ring passage 417A. The vacuum ring 417creates a vacuum connection with the corneal surface 2A to fix theenergy conducting element 411 to the corneal surface 2A. The vacuum ring417 may include an interior channel 417C which is operably connected tothe vacuum source 430 via connection port 417B. The vacuum ring 417 mayalso include a plurality of openings 417D which open the interiorchannel 417B to the corneal surface 2A. Therefore, when the openings417D are positioned in contact with the corneal surface 2A and thevacuum source 430 is activated to create a near vacuum or low pressurewithin the interior channel 417C, the openings 417D operate to suctionthe vacuum ring 417 and the applicator 410 to the corneal surface 2A. Inthis case, the vacuum source 430 may be a syringe or similar device.

In some embodiments, the energy conducting element 411 and the vacuumring 417 may be separate components which may be detachably coupled toeach other. Thus, as shown in FIG. 7A, a separate energy conductingelement 411 may be slidingly received by the vacuum ring 417 into thecoaxial position. Any coupling technique, such as a mechanicalattachment, may be employed to keep the energy conducting element 411stably positioned within the vacuum ring 417. The vacuum ring 417 may bepositioned on the corneal surface 2A before it receives the energyconducting element 411, or alternatively, the electrical conductingelement 411 may be combined with the vacuum ring 417 before thecombination is positioned on the corneal surface 2A.

In alternative embodiments, the energy conducting element 411 and thevacuum ring 417 may be non-detachably fixed to each other.

Other aspects of the embodiment of FIG. 7 are similar to the embodimentsdescribed previously. In particular, as FIG. 7 illustrates, theapplicator 410 also employs a micro-controlled coolant delivery system412 as well as a coolant supply 413. The coolant delivery element 412may employ a nozzle structure 412A with an opening 412B directed at thedistal end 410B. A solenoid valve, or other actuator, may be employed tocreate the pulses of coolant. The controller 440 may electronicallycontrol the solenoid valve, or other actuator, to deliver the coolant tothe corneal surface 2A. As such, the micro-controlled coolant deliverysystem 412, which is in fluid communication with the coolant supply 413,operates in a manner similar to the coolant delivery system 12 inFIG. 1. In other words, pulses of coolant, or cryogen, from the coolantsupply 413 are preferably applied to the corneal surface 2A before andafter the energy is applied to the cornea 2.

The embodiments described herein may all employ sensors to measurephysical variables of the eye. For example, in one embodiment, FIG. 1depicts a plurality of sensors 16 which are discretely positioned at andabout the distal end 10B of the applicator 10. The sensors may beoperably connected to the controller 40 (not shown) to allow the data tobe stored and/or communicated to operators. As a further example, theembodiment of FIGS. 7A and 7B employs an arrangement of sensors 416 onthe vacuum ring 417 as the vacuum ring 417 makes direct contact with thecorneal surface 2A. In other embodiments, sensors may be more broadlyincorporated into a surface at the distal end of the applicator, such asthe dielectric layer 110D in FIG. 2. Typically, the sensors are placedin contact with the cornea and provide measurements for various areas ofthe cornea. In general, the sensors may include devices that are formedas parts of the applicator and/or external devices that are separatefrom the applicator. The sensors may be microelectronic devices,including, but not limited to, infrared detectors that measuretemperature, thin film or microelectronic thermal transducers,mechanical transducers such as a piezoresistive or piezoelectricdevices, or force-sensitive quartz resonators that quantify cornealelongation or internal pressure.

In general, the sensors may provide information that is used to preparethe systems before treatment, provide feedback during treatment toensure proper application of treatment, and/or measure the results ofthe treatment.

The cornea and eye have one or more variable physical properties thatmay be affected by the application of energy and the resulting increasein temperature. The sensors may directly or indirectly measure thesephysical variables and provide a sensor signal to processing circuitry,such as the controllers 40, 140, 240, and 340 described above. Thecontroller may analyze the measurements to determine if and when thetreatment has achieved the desired effects. Processing circuitry mayalso generate a stop signal that terminates treatment when a specifiedphysical variable achieves a predetermined value or falls within apredetermined range. In some embodiments, to avoid thermal damage to thecorneal epithelium, and the endothelium, program instructions for thecontroller may include a safety mechanism that generates a stop signalwhen the application of heat energy exceeds certain parameters, e.g.time limits.

The embodiments described herein may also include disposable andreplaceable components, or elements, to minimize cross-contamination andto facilitate preparation for procedures. In particular, components thatare likely to come into contact with the patient's tissue and bodilyfluids are preferably discarded after a single use on the patient tominimize cross-contamination. Thus, embodiments may employ one or moreuse indicators which indicate whether a component of the system has beenpreviously used. If it is determined from a use indicator that acomponent has been previously used, the entire system may be preventedfrom further operation so that the component cannot be reused and mustbe replaced.

For example, in the embodiment of FIG. 1, a use indicator 50 is employedto record usage data which may be read to determine whether theapplicator 10 has already been used. In particular, the use indicator 50may be a radio frequency identification (RFID) device, or similar datastorage device, which contains usage data. The controller 40 may readand write usage data to the RFID 50. For example, if the applicator 10has not yet been used, an indicator field in the RFID device 50 maycontain a null value. Before the controller 40 delivers energy from theenergy source 20 to the energy conducting element 11, it reads the fieldin the RFID device 50. If the field contains a null value, thisindicates to the controller 40 that the applicator 10 has not been usedpreviously and that further operation of the applicator 10 is permitted.At this point, the controller 40 writes a value to the field in the RFIDdevice 50 to indicate that the applicator 10 has been used. When acontroller 40 later reads the field in the RFID device 50, the non-nullvalue indicates to the controller 40 that the applicator 10 has beenused previously, and the controller will not permit further operation ofthe applicator 10. Of course, the usage data written to the RFID device50 may contain any characters or values, or combination thereof, toindicate whether the component has been previously used.

In another example, where the applicator 410 and the vacuum ring 417 inthe embodiment of FIG. 7A are separate components, use indicators 450Aand 450B may be employed respectively to indicate whether theapplication 410 or the vacuum ring 417 has been used previously. Similarto the use indicator 50 described previously, the use indicators 450Aand 450B may be RFID devices which the controller 440 may accessremotely to read or write usage data. Before permitting operation of theapplicator 410, the controller 40 reads the use indicators 450A and450B. If the controller 440 determines from the use indicators 450A and450B that the applicator 410 and/or the vacuum ring 417 have alreadybeen used, the controller 440 does not proceed and does not permitfurther operation of the applicator 410. When the applicator 410 and thevacuum ring 417 are used, the controller 440 writes usage data to bothuse indicators 450A and 450B indicating that the two components havebeen used.

In operation, a physician or other operator manually accesses a device,such as a computer keyboard, that interfaces with a controller, such asthe controllers 40, 149, 240, and 340. The interface enables theoperator to set up and/or initiate treatment. The system may requestinput, such as a predetermined amount of diopter correction that isrequired for a particular patient, baseline measurements of physicalvariables, astigmatism measurements, parameters for energy conduction tothe cornea, timing and sequence information for the application of heatenergy and pulses of coolant, and/or target values for physicalvariables that will be modified by treatment. The controller acceptsprogram instructions that may access user input data or programselections from the interface and causes the system to implement aselected vision correction treatment.

In general, the controller may be a programmable processing device thatexecutes software, or stored instructions, and that may be operablyconnected to the devices described above. In general, physicalprocessors and/or machines employed by embodiments of the presentinvention for any processing or evaluation may include one or morenetworked or non-networked general purpose computer systems,microprocessors, field programmable gate arrays (FPGAs), digital signalprocessors (DSPs), micro-controllers, and the like, programmed accordingto the teachings of the exemplary embodiments of the present invention,as is appreciated by those skilled in the computer and software arts.The physical processors and/or machines may be externally networked withthe image capture device, or may be integrated to reside within theimage capture device. Appropriate software can be readily prepared byprogrammers of ordinary skill based on the teachings of the exemplaryembodiments, as is appreciated by those skilled in the software art. Inaddition, the devices and subsystems of the exemplary embodiments can beimplemented by the preparation of application-specific integratedcircuits (ASICs) or by interconnecting an appropriate network ofconventional component circuits, as is appreciated by those skilled inthe electrical art(s). Thus, the exemplary embodiments are not limitedto any specific combination of hardware circuitry and/or software.

Stored on any one or on a combination of computer readable media, theexemplary embodiments of the present invention may include software forcontrolling the devices and subsystems of the exemplary embodiments, fordriving the devices and subsystems of the exemplary embodiments, forenabling the devices and subsystems of the exemplary embodiments tointeract with a human user, and the like. Such software can include, butis not limited to, device drivers, firmware, operating systems,development tools, applications software, and the like. Such computerreadable media further can include the computer program product of anembodiment of the present inventions for performing all or a portion (ifprocessing is distributed) of the processing performed in implementingthe inventions. Computer code devices of the exemplary embodiments ofthe present inventions can include any suitable interpretable orexecutable code mechanism, including but not limited to scripts,interpretable programs, dynamic link libraries (DLLs), Java classes andapplets, complete executable programs, and the like. Moreover, parts ofthe processing of the exemplary embodiments of the present inventionscan be distributed for better performance, reliability, cost, and thelike.

Common forms of computer-readable media may include, for example, afloppy disk, a flexible disk, hard disk, magnetic tape, any othersuitable magnetic medium, a CD-ROM, CDRW, DVD, any other suitableoptical medium, punch cards, paper tape, optical mark sheets, any othersuitable physical medium with patterns of holes or other opticallyrecognizable indicia, a RAM, a PROM, an EPROM, a FLASH-EPROM, any othersuitable memory chip or cartridge, a carrier wave or any other suitablemedium from which a computer can read.

While various embodiments in accordance with the present invention havebeen shown and described, it is understood that the invention is notlimited thereto. The present invention may be changed, modified andfurther applied by those skilled in the art. Therefore, this inventionis not limited to the detail shown and described previously, but alsoincludes all such changes and modifications.

What is claimed is:
 1. A system for applying therapy to an eye, thesystem comprising: an energy source; a conducting element operablyconnected to the energy source and extending from a proximal end of theconducting element to a distal end of the conducting element, theconducting element adapted to direct energy from the energy source tothe distal end; a coolant supply; at least one coolant delivery elementin communication with the coolant supply; and a sheet of dielectricmaterial covering the distal end to provide a bottom surface of asubstantially enclosed assembly that includes at least the conductingelement and the coolant delivery system, the coolant delivery elementbeing adapted to deliver a micro-controlled pulse of coolant to thedielectric material.
 2. The system according to claim 1, wherein theconducting element includes an outer conductor and an inner conductor,the outer conductor and the inner conductor being separated by a gap. 3.The system of claim 2, wherein the inner conductor includes at least onecoolant delivery opening coupled to the coolant delivery system, the atleast one coolant delivery opening configured to deliver coolant towardthe distal end.
 4. The system of claim 3, wherein the at least onecoolant delivery opening comprises a plurality of coolant deliveryopenings equally spaced around an exterior surface of the innerconductor.
 5. The system of claim 3, wherein the at least one coolantdelivery opening comprises a plurality of coolant delivery openingsarranged in at least two concentric circles on the inner conductor. 6.The system of claim 3, wherein the inner conductor includes afrustoconical interior structure disposed centrally within a hollowportion.
 7. The system of claim 6, wherein the inner conductor furtherincludes at least one channel coupling the at least one coolant deliveryopening to the coolant delivery system.
 8. The system of claim 7,wherein the at least one channel and the at least one coolant openingare disposed on an angled surface of the frustoconical structure.
 9. Thesystem of claim 2, wherein the coolant delivery system is disposed inthe gap between the outer conductor and the inner conductor.
 10. Thesystem according to claim 1, further comprising a vacuum source and atleast one vacuum channel connected to the vacuum source, the at leastone vacuum channel having an opening positioned at the distal end. 11.The system according to claim 10, wherein the vacuum channel opening isadapted to engage the eye and position the distal end relative to afeature of the eye.
 12. The system according to claim 10, wherein thevacuum channel opening is adapted to draw away the coolant delivered bythe at least one coolant delivery element.
 13. The system according toclaim 1, further comprising a vacuum source coupled to at least onevacuum channel, the at least one vacuum channel having an openingpositioned at the distal end and the vacuum source being operable tolower the pressure at the distal end.
 14. The system according to claim1, wherein the sheet of dielectric material has a varying dielectricconstant.
 15. The system according to claim 1, wherein the sheet ofdielectric material has a variable thickness.
 16. A system for applyingtherapy to an eye, the system comprising: an energy source; a conductingelement operably connected to the energy source and extending from aproximal end of the conducting element to a distal end of the conductingelement, the conducting element adapted to direct energy from the energysource to the distal end, the conducting element including an outerconductor and an inner conductor, the outer conductor being separatedfrom the inner conductor by a gap; a coolant supply; at least onecoolant delivery element in communication with the coolant supply; asheet of dielectric material covering the distal end to provide a bottomsurface of a substantially enclosed assembly that includes at least theconducting element and the coolant delivery system, the coolant deliveryelement being adapted to deliver a micro-controlled pulse of coolant tothe dielectric material, at least one of a distal end of the outerconductor and a distal end of the inner conductor being in directcontact with the sheet of dielectric material; and a controllercommunicatively coupled to the energy source and the at least onecoolant delivery element, the controller operable to control delivery ofenergy from the energy source to the conducting element, the controllerfurther operable to control delivery of the coolant from the at leastone coolant delivery element to the dielectric material.
 17. The systemaccording to claim 16, wherein the controller is configured to cause theat least one coolant delivery element to deliver a pulse of coolant tothe dielectric material to evaporatively cooling the eye.
 18. The systemaccording to claim 16, wherein the controller is configured to determinethe amount and timing of coolant delivered from the at least one coolantdelivery element.
 19. The system according to claim 16, wherein theinner conductor has an outer diameter of approximately 2 mm toapproximately 10 mm and an inner diameter of approximately 2.1 mm toapproximately 12 mm.
 20. The system according to claim 16, wherein theinner conductor includes a hollow portion defined by a concave,substantially semi-spherical surface within the inner conductor, theinner conductor further includes at least one vent configured to controlthe pressure within the hollow portion.